Heteroatom-Doped Perihexacene from a Double Helicene Precursor:
On-Surface Synthesis and Properties
† ‡ ‡ ‡ ⊥ ‡ ‡ ‡ ‡ ⊗ ⊗ # ⊥ ‡ ∥ ‡ ∇ † † † ‡ ⊥ ⊗ # ∥ ∇
1. General Method
All commercially available chemicals were used without further purification unless otherwise noted. Column chromatography was done with silica gel (particle size 0.063-0.200 mm) and thin layer chromatography (TLC) was performed on silica gel-coated aluminum sheets with F254 indicator. All yields given refer to isolated yields. Nuclear magnetic resonance (NMR) spectra were recorded on an AVANCE 300 MHz Bruker spectrometer. Chemical shifts were reported in ppm. Coupling constants (J values) were reported in Hertz. 1H NMR chemical shifts were referenced to CHDCl2 (5.320 ppm) or C2HDCl4 (6.000 ppm). 13C NMR chemical shifts were referenced to CD2Cl2 (54.00 ppm). The attached proton test (APT) technique of 13C NMR (J-modulated spin-echo for 13C-nuclei coupled to 1H-nuclei) was used to distinguish the carbon atoms with even or odd number of attached protons. The quaternary (C) and methylene (CH2) signals were in the upper phase and the methine (CH) and methyl (CH3) signals were in the opposite phase. Field desorption mass spectrometry (FD-MS) was carried out on a VG-Instrument ZAB 2-SE-FDP. High-resolution mass spectrometry (HRMS) was performed either on a Q-Tof Ultima 3 (micromass/Waters) by electrospray ionization (ESI) or on a SYNAPT G2 Si high resolution time-of-flight mass spectrometer (Waters Corp., Manchester, UK) by matrix-assisted laser desorption/ionization (MALDI) with tetracyanoquinodimethane (TCNQ) as the matrix.Absorption spectra were recorded on a Perkin-Elmer Lambda 900 spectrophotometer. Photoluminescence spectra were recorded on a J&MTIDAS spectrofluorometer. The photoluminescence quantum yield (ΦF) was measured with 9,10-diphenylanthracene as a standard.1
All surface-assisted experiments were performed in ultrahigh vacuum (UHV) chambers with a base pressure of 10–11 mbar. The Au(111) single crystal was cleaned by sputtering (Ar+, 1 keV) and annealing up to 750 K. The precursor 2 was thermally evaporated onto the Au(111) surface held at room temperature. The sublimation temperature of precursor 2 is 635 K.
Scanning tunneling microscopy (STM) and atomic force microscopy (AFM) experiments were carried out with a low-temperature scanning probe microscopy
system (LT-SPM, ScientaOmicron, Germany) at a temperature of 4.9 K. Scanning tunneling spectra (dI/dV) were detected with a lock-in amplifier (HF2LI by Zurich Instruments, Switzerland). Commercial Qplus sensors2 equipped with tungsten tips (resonance frequency = 22350 Hz, Q-factor = 11000; tunneling current separated, ScientaOmicron) were used for non-contact AFM (nc-AFM) measurements. Repeated indentation to the substrate was used to shape the apex of the tip prior to the pick-up of a CO molecule from the sample.3 Frequency-shift images at constant height with the CO-sensitized tip were performed with an amplitude of 100 pm.
X-ray photoelectron spectroscopy (XPS) measurements were performed on the PEARL beamline of the SLS synchrotron radiation facility (Villigen, Switzerland), using linearly polarized radiation with photon energy of 425 eV.4 After deposition at room temperature, the sample was then transferred into the analysis chamber where the fast-XPS map was recorded during the in-situ annealing of the sample. High-resolution XPS (HR-XPS) spectra were recorded before and after the temperature ramp. XPS spectra were obtained in normal emission geometry, using a hemispherical electron analyzer equipped with a multichannel plate (MCP) detector. HR-XPS spectra were recorded in “sweep” mode with 20 eV pass energy, while the fast-XPS measurement was performed using the “fix” mode (snapshots of the C 1s level) acquiring one spectrum every 5 s with 50 eV pass energy.
Raman spectroscopy was performed in a Bruker Senterra Raman Microscope using a 532 nm laser (corresponding to 2.33 eV excitation energy). The Raman spectra of the perihexacene analogue 1 were acquired using three scans of 60 seconds adopting 2 mW laser irradiation power; the Raman spectra of the precursor 2 were acquired using a single scan of 10 seconds adopting 0.2 mW laser irradiation power. In both cases a 50× objective lens was used, which results in a 1-2 μm spot size. The Raman spectrum of 1 was measured on the Au(111) surface, while the Raman spectrum of 2 was measured on the powder sample.
2. Procedures of Solution Synthesis
2-Bromo-3-methoxynaphthalene (4).5 To a solution of 2-methoxynaphthalene (15.8 g, 100 mmol) in dry THF (120 mL) was added n-BuLi (1.60 M in hexane, 66.0 mL, 106 mmol) at –78 °C under argon. After the mixture was stirred at room temperature for 1 h, 1,2-dibromoethane (20.7 g, 110 mmol) was added at –78 °C. The resulting mixture was then stirred at room temperature for 24 h before quenching by an aqueous NH4Cl solution. The mixture was extracted with ether (30 mL × 3) and the combined organic layers were washed with brine and water and dried over MgSO4. After removal of the solvent under reduced pressure, the residue was purified by recrystallization from hexane to give 17.5 g of compound 4 (74%) as a white solid. 1H NMR (300 MHz, CD2Cl2, 298 K, ppm) δ 8.07 (s, 1H), 7.75 (dd, J = 8.3, 1.4 Hz, 1H), 7.71 (dd, J = 8.1, 1.4 Hz, 1H), 7.47 (ddd, J = 8.3, 6.9, 1.4 Hz, 1H), 7.37 (ddd, J = 8.1, 6.9, 1.4 Hz, 1H), 7.20 (s, 1H), 3.99 (s, 3H). 13C NMR (75 MHz, CD2Cl2, 298 K, ppm) δ 154.16, 134.20, 132.74, 129.96, 127.30, 127.21, 127.14, 125.04, 113.82, 107.27, 56.76. FD-MS (8 kV) m/z: Calcd for C11H9BrO: 236.0; Found: 235.9 (100%) [M]+.
1,4-Diiodo-2,3,5,6-tetra(3-methoxynaphthalen-2-yl)benzene (5). To a Schlenk flask containing activated Mg (480 mg, 20.0 mmol) and 5 mL of dry THF was slowly added a solution of 2-bromo-3-methoxynaphthalene (4) (3.79 g, 16.0 mmol) in 20 mL of dry THF. After the mixture was stirred at 60 °C for 2 h, the generated Grignard reagent was transferred into a Schlenk tube charged with hexabromobenzene (1.10 g,
2.00 mmol) under argon and the resulting mixture was stirred at 80 °C for 24 h. Iodine (3.05 g, 12.0 mmol) was added at 0 °C and the reaction mixture was stirred at room temperature for 2 h. After quenching with water, the mixture was extracted with chloroform for three times. The combined organic layers were washed with brine and water and dried over MgSO4. After removal of the solvents under reduced pressure, the residue was purified by column chromatography over silica gel (eluent: hexane/CH2Cl2 = 1 : 1), and then sonicated in 3 mL of toluene, filtrated, and washed with hexane to give 496 mg (26%) of compound 5 as a white solid. 1H NMR (300 MHz, C2D2Cl4, 298 K, ppm) δ 8.04 – 6.25 (m, 24H, aromatic signals of stereoisomers), 4.20 – 3.45 (m, 12H, methyl signals of stereoisomers). HRMS (ESI) m/z: Calcd for C50H37O4I2: 955.0781; Found: 955.0767 [M + H]+.
12a,26a-Dibora-12,13,26,27-tetraoxa-benzo[1,2,3-hi:4,5,6-h'i']dihexacene (2). To a solution of compound 5 (0.14 g, 0.15 mmol) in anhydrous chlorobenzene (10 mL) was added t-BuLi (1.7 M in hexane, 0.35 mL, 0.60 mmol) at −45 °C under argon. After stirring at 0 °C for 3 h, BBr3 (1.0 M in heptane, 0.40 mL, 0.40 mmol) was added at −45 °C. The reaction mixture was stirred at 40 °C for 24 h. After quenching with methanol, the precipitate was filtrated and washed thoroughly with methanol, water, acetone, dichloromethane, and hexane, to afford 43 mg (43%) of compound 2 as a yellow solid. The solubility of 2 in CD2Cl2, CDCl3, 1,1,2,2,-tetrachloroethane-d4, toluene-d8, DMSO-d6, etc. was extremely low, so that even an 1H NMR spectrum could not be recorded at high temperatures (up to 140 °C). HRMS (MALDI) m/z: Calcd for C46H24B2O4: 662.1861; Found: 662.1876 [M]+.
3. Photophysical Properties
Figure S1. Absorption and emission spectra of 2 in C2H2Cl4 solutions. The absorption maximum is at 345 nm (absorption coefficient: 6.9 × 104 M−1 cm−1). The absorption onset is at 487 nm, corresponding to an optical energy gap of 2.55 eV. According to time-dependent density functional theory (TD-DFT) calculations, the lowest energy absorption is assigned to the HOMOLUMO transition, whereas the absorption maximum is mainly contributed to by the HOMO−5LUMO transition (Figure S7). A green-yellow fluorescence was observed for compound 2, with an emission maximum at 490 nm and a quantum yield (ΦF) of 3%.
4. Scanning Tunneling Microscopy
Figure S2. (a) STM image of precursor 2 deposited on Au(111) held at room temperature (tunneling parameters: –2.0 V, 100 pA). (b) STM image of product 1 after annealing to 380 °C (tunneling parameters: 0.6 V, 20 pA).
Figure S3. Separation analysis for neighboring perihexacene analogue 1 on Au(111). (a) Distribution map for 326 molecule pairs. (b) Histogram of the vertical separation, with highlighted areas for “abreast” (red) and “stepped” arrangement (blue). (c) Horizontal distribution of molecules in the two regions highlighted in (b) with the corresponding Gauss fits (stepped assembly in blue, abreast assembly in red). Molecular models of (d) the stepped arrangement and (e) the abreast arrangement with vertical and horizontal separation distances. The peripheral short bonds indicate C−H bonds where the hydrogen atoms are omitted for clarity.
Both species, precursor 2 and perihexacene analogue 1, assemble into chains on the Au(111) surface (Figure S2). In the case of the latter the arrangement along each chain occurs in two different fashions, namely the “stepped” and the “abreast” arrangement. To investigate the differences for the two packing schemes in more detail, we measured the distances within all chains in an STM image of 120 × 120 nm2 (containing 73 chains, i.e., dimers to oligomers, incorporating 326 separations). Figure S3a shows the distribution map of the horizontal separation (along the chain) and the vertical separation (perpendicular to the chain) between neighboring molecules. Three distinct areas can be observed. Integrating the number of molecules with the same vertical separation reveals three clear maxima assignable to the abreast and the stepped arrangements, highlighted in red and blue, respectively (Figure S3b). A Gauss fit to the latter reveals an average separation of 0.5 nm, corresponding to an upshift of approximately two zigzag cusps, which can be associated with the formation of four O···H hydrogen bonds (up and down shifts are equivalent in case of the symmetric molecule). Next, the distances of the two species are analyzed for their horizontal separation. Figure S3c shows the two histograms and the corresponding fits to the data points, revealing a separation of 1.036 nm for the stepped and 1.125 nm for the abreast arranged molecules. With this information the bond length of the O···H hydrogen bonds present in the stepped case can be determined to be 0.19 nm and the O···O distance in the abreast case 0.40 nm. The latter translates into an O···Au distance of 0.235 nm for the coordinating Au adatom, which is well within the range expected for metal coordination.
5. Scanning Tunneling Spectroscopy
Figure S4. Differential conductance (dI/dV) spectra (c) of precursor 2 and perihexacene analogue 1 with the corresponding positions indicated in the STM images (a,b). Tunneling parameters: (a) 300 mV, 100 pA; (b) 100 mV, 30 pA.
6. Fast XPS Mapping
Figure S5. Fast XPS mapping for the C 1s level of 2 deposited on Au(111) and annealed with a heating rate of 0.2 °C s−1 (central panel, pass energy = 50 eV). High-resolution C 1s spectra (pass energy = 20 eV) acquired before and after the heating ramp (top and bottom panels) together with representative schemes of the molecule in the two phases. Vertical profiles representing the change of the C–C and C–H components (blue and orange, respectively) are reported in the right panel. The C–O component (green) and the total area of each spectrum (black) are not significantly changing during the annealing, as shown by the curves reported in the left panel.
7. Theoretical Simulations
7.1 Gas-phase quantum chemistry calculations. The geometries were optimized in the gas phase at the B3LYP/6-311G(d,p) level of theory using the Gaussian 09 software package.6 Frequencies were calculated for each geometry to confirm the local energy minimum or the transition state. The rate constant (k) at room temperature (298.15 K) was estimated using the Eyring equation7
k = κ(kBT/h)exp(−ΔG⧧/RT)
where k is the rate constant; κ is the transmission coefficient which is taken to be unity; kB is the Boltzmann constant; T is the temperature; h is the Planck constant; ΔG⧧ is the Gibbs energy of activation; R is the gas constant.
Figure S6. Isomerization process of compound 2 from the twisted to the anti-folded conformation. The relative Gibbs free energies were calculated at the B3LYP/6-311G(d,p) level. As estimated from the Eyring equation, the rate constants for the forward isomerization (kf, from twisted 2 to anti-foled 2) and the backward reaction (kb, from anti-folded 2 to twisted 2) are 4.7 × 10−5 s−1 and 5.8 × 10−1 s−1, respectively. Therefore, the thermodynamic equilibrium constant K (= kf/kb) of the forward reaction is 8.1 × 10−5, indicating that compound 2 dominantly adopts the twisted conformation at the equilibrium state at room temperature.
Figure S7. (a) The simulated absorption spectrum of compound 2 (Gaussian line shape, half-width: 0.15 eV) and the oscillator strengths (blue bars) by TDDFT calculations at the B3LYP/6-311G(d,p) level. The twisted conformation was used since it dominantly exists at the equilibrium state. (b) Selected molecular orbitals and energy levels of 2 calculated at the B3LYP/6-311G(d,p) level. H: HOMO; L: LUMO.
Table S1. Selected electronic transitions of 2 calculated by TDDFT method.
Excited State Energy (eV) Wavelength (nm) Oscillator Strength Configuration 1 2.57 483 0.1258 HOMO→LUMO (0.70534) 2 2.96 420 0.1121 HOMO–1→LUMO (0.69904) 3 3.24 383 0.4612 HOMO–5→LUMO (–0.14374) HOMO–4→LUMO (0.47269) HOMO→LUMO+1 (0.48195) 4 3.67 338 0.9707 HOMO–5→LUMO (0.59951) HOMO–1→LUMO+1 (0.24188) HOMO→LUMO+1 (0.14698) HOMO→LUMO+4 (–0.11746)
Figure S8. Frontier molecular orbitals of compounds 2 and 1 and associated energy levels according to DFT calculations at the B3LYP/6-311G(d,p) level, showing that 1 has a lower HOMO-LUMO gap than 2. H: HOMO; L: LUMO.
7.2 On-Surface Simulations. DFT calculations were performed using the Vienna Ab initio simulation package (VASP)8 using the projector augmented wave (PAW) method9 and the optB86b-vdW functional, which includes long-range van der Waals (vdW) interactions.10 Considering the large size of the supercells, the k-point sampling was restricted to the Γ point. A plane-wave cutoff of 400 eV was used. The vacuum regions in all the calculations were larger than 10 Å. We used a four layer thick rectangular 8×5 Au(111) slab in the calculations involving isolated molecules while a four layer thick rectangular 8×4 Au(111) slab was used in the calculations involving hydrogen bonded chains of precursor 2. The smallest distance between any two atoms in a molecule and its periodic image was larger than 4.5 Å, ensuring minimal interaction.
The energy barriers for the isomerization process of precursor 2 from the twisted to the anti-folded conformation were calculated using the climbing-image nudged elastic band (NEB) method.11 We used 16 intermediate structures in our NEB calculations. The bottom two layers in the Au slab were fixed throughout the NEB
calculations while remainder of the atomic coordinates were relaxed using a conjugate-gradient algorithm until all forces were smaller in magnitude than 0.05 eV/Å.
Table S2. Energetics of precursor 2 as single molecules.a
Total energy (eV) Binding energy (eV) Gas phase Substrate-supported
T -482.73 -659.79 3.75
A -482.55 -659.82 3.96
a
T: twisted conformation of 2; A: anti-folded conformation of 2.
Table S3. Energetics of hydrogen bonded chains of precursor 2.a
Total energy (eV) Binding energy (eV) Gas phase Substrate-supported
TT -966.12 -1065.59 7.31
AA -965.52 -1065.88 8.20
a
The chains are labeled as TT or AA depending on the conformations of the monomers in the smallest repeating units. The energies shown in this table are for the repeating units, that is, the dimers TT and AA.
Table S4. Binding energies of hydrogen-bonds in chains of precursor 2.a Gas phase Substrate-supported
TT 0.71 0.70
AA 0.61 0.75
a
The chains are labeled as TT or AA depending on the conformations of the monomers in the smallest repeating units.
Figure S9. Atomistic schematics of the hydrogen-bonded chains of precursor 2 in the (a) gas-phase and (b) substrate-supported configurations. Hydrogen bonds are depicted by black dashed lines.
Figure S10. Atomistic schematic of perihexacene analogue 1 (left) and its DFT-simulated STM image (right).
7.3 Assignment of the Main Raman Transitions. The DFT calculations of the Raman spectra of 1 and 2 reported in the main text have been carried out at the B3LYP/6-31G(d,p) level in pre-resonance conditions by using the Gaussian 09 program6 and by adopting the excitation wavelengths of 520 nm (1) and 530 nm (2). These wavelengths were selected because they best reproduced the experimental
observation after systematic inspection of the results of the simulations carried out over a wide range of excitation wavelengths (400–560 nm). The selected wavelengths are both close to the excitation wavelength adopted in the experiments (532 nm). The slight difference between the excitation wavelength selected for 1 vs. 2 (i.e., 520 vs. 530 nm) can be ascribed to the different experimental conditions adopted for recording the spectra of the two molecules (1 adsorbed on gold vs. 2 as powder). As customary, wavenumbers in all simulated spectra have been uniformly scaled by 0.98 to ease the comparison with experiments. The twisted conformation of 2 was used for these simulations since this is the expected structure of the molecule in the measured powder samples.
Figure S11. Simulated Raman spectra of (a) 1 and (b) 2 as a function of the excitation wavelength. The spectra selected for Figure 3 in the main text are drawn with green lines. The observed line shape of the G band of 1 is the result of an excitation located around 520-530 nm: a weak G signal is obtained for excitations below 500 nm, and above 530 nm the line shape of the G band significantly deviates from the experimental observation. In contrast, the relative intensities of the simulated spectra of 2 are less affected by the choice of the excitation wavelength around 530 nm.
Figure S12. Assignment of the D modes of 1 and 2 based on the nuclear displacements computed for graphene (adapted from the literature12). Red arrows (or sticks) represent displacement vectors; CC bonds are represented as green (blue) lines of different thickness according to their relative stretching (shrinking).
Figure S13. Assignment of the G modes of 1 and 2 based on the nuclear displacements computed for graphene (adapted from the literature12). Red arrows (or sticks) represent displacement vectors; CC bonds are represented as green (blue) lines of different thickness according to their relative stretching (shrinking).
Figure S12 and S13 show the nuclear displacements of the normal modes of 1 and 2 assigned to the relevant observed Raman lines. The D modes of 1 and 2 are
computed respectively at 1479 and 1378 cm-1; the associated nuclear displacement patterns at the center of the molecule closely match the characteristic D mode of graphene (Figure S12). Interestingly, the Raman spectrum of 2 shows one transversal G mode (Gt, computed at 1572 cm-1) and one longitudinal G mode (Gl, computed at 1683 cm-1). This naming scheme has been adopted after inspecting the direction of the displacements of the π-conjugated carbon atoms with respect to the shape of the molecule (Figure S13). In molecule 1 the observed G peak is longitudinal (computed at 1659 cm-1) and the associated transversal component (computed at 1677 cm-1) is comparatively weak. The latter is predicted and observed as the higher wavenumber shoulder of the G line (see Figure 3 in the main text). Based on DFT calculations, the lower wavenumber shoulder of the G line of 1 is computed at 1643 cm-1 and the associated normal mode displays a collective ring stretching pattern not directly related with graphene G mode.
Appendix:
Cartesian coordinates obtained in gas-phase DFT calculations at the B3LYP/6-311G(d,p) level Optimized twisted 2 Tag Symbol X Y Z 1 C -1.240631 0.696511 0.146523 2 C -1.240631 -0.696511 -0.146525 3 C 0.000007 -1.353736 -0.000012 4 C 1.240644 -0.696513 0.146513 5 C 1.240645 0.696514 -0.146514 6 C 0.000007 1.353736 0.000011 7 C -2.372390 1.507763 0.638123 8 C 2.372399 1.507775 -0.638111 9 C -2.275227 2.939906 0.661540 10 C -3.299037 3.728744 1.127589 11 C -4.475701 3.157127 1.656370 12 C -4.567064 1.730525 1.723302 13 C -3.505948 0.952830 1.216840 14 C 3.505953 0.952855 -1.216850 15 C 4.567063 1.730559 -1.723307 16 C 4.475700 3.157160 -1.656349 17 C 3.299039 3.728766 -1.127549 18 C 2.275234 2.939918 -0.661506 19 C -2.372390 -1.507764 -0.638124 20 C 2.372399 -1.507775 0.638110 21 C 2.275235 -2.939918 0.661501 22 C 3.299040 -3.728766 1.127544 23 C 4.475699 -3.157160 1.656348 24 C 4.567061 -1.730559 1.723311 25 C 3.505950 -0.952855 1.216853 26 C -3.505951 -0.952830 -1.216837 27 C -4.567067 -1.730525 -1.723298 28 C -4.475702 -3.157127 -1.656371 29 C -3.299036 -3.728744 -1.127595 30 C -2.275225 -2.939906 -0.661547 31 B 0.000005 2.880034 0.000021 32 B 0.000007 -2.880034 -0.000027 33 O -1.140006 3.590827 0.249379 34 O 1.140012 3.590832 -0.249334 35 O -1.140003 -3.590827 -0.249390 36 O 1.140015 -3.590832 0.249324
37 C -5.553233 3.937817 2.152209 38 C -6.663181 3.335707 2.690902 39 C -6.752729 1.923357 2.764028 40 C -5.729201 1.140860 2.293168 41 C -5.729207 -1.140860 -2.293159 42 C -6.752734 -1.923357 -2.764019 43 C -6.663184 -3.335707 -2.690898 44 C -5.553234 -3.937817 -2.152209 45 C 5.553226 -3.937860 2.152183 46 C 6.663168 -3.335761 2.690901 47 C 6.752714 -1.923412 2.764057 48 C 5.729191 -1.140906 2.293202 49 C 5.729196 1.140905 -2.293194 50 C 6.752719 1.923412 -2.764049 51 C 6.663171 3.335760 -2.690897 52 C 5.553227 3.937859 -2.152183 53 H -3.168290 4.804239 1.108007 54 H -3.591124 -0.123331 1.286069 55 H 3.591128 -0.123305 -1.286102 56 H 3.168289 4.804260 -1.107950 57 H 3.168292 -4.804261 1.107942 58 H 3.591124 0.123305 1.286108 59 H -3.591128 0.123331 -1.286062 60 H -3.168286 -4.804239 -1.108017 61 H -5.483753 5.019157 2.101086 62 H -7.479659 3.942113 3.066664 63 H -7.635847 1.464603 3.193682 64 H -5.794643 0.059166 2.343221 65 H -5.794650 -0.059165 -2.343208 66 H -7.635854 -1.464602 -3.193669 67 H -7.479663 -3.942112 -3.066659 68 H -5.483753 -5.019157 -2.101091 69 H 5.483747 -5.019199 2.101038 70 H 7.479642 -3.942173 3.066659 71 H 7.635827 -1.464667 3.193731 72 H 5.794632 -0.059212 2.343278 73 H 5.794639 0.059212 -2.343266 74 H 7.635833 1.464666 -3.193719 75 H 7.479645 3.942173 -3.066655 76 H 5.483746 5.019199 -2.101042 Optimized anti-folded 2 Tag Symbol X Y Z 1 C -1.251802 0.701919 -0.103978 2 C -1.251802 -0.701921 0.103975 3 C 0.000001 -1.334466 0.272765 4 C 1.251803 -0.701921 0.103975 5 C 1.251803 0.701920 -0.103977 6 C 0.000000 1.334465 -0.272767 7 C -2.422582 1.614656 -0.073800 8 C 2.422582 1.614657 -0.073795 9 C -2.338269 2.899367 -0.705748 10 C -3.399065 3.771292 -0.725974 11 C -4.600765 3.467346 -0.050888 12 C -4.675029 2.241460 0.682978 13 C -3.576392 1.356166 0.650551 14 C 3.576392 1.356166 0.650556 15 C 4.675028 2.241460 0.682986 16 C 4.600765 3.467347 -0.050877 17 C 3.399066 3.771295 -0.725964 18 C 2.338270 2.899369 -0.705740 19 C -2.422582 -1.614658 0.073797 20 C 2.422582 -1.614658 0.073794 21 C 2.338271 -2.899370 0.705740 22 C 3.399067 -3.771294 0.725964 23 C 4.600767 -3.467346 0.050878 24 C 4.675030 -2.241459 -0.682985 25 C 3.576392 -1.356166 -0.650557 26 C -3.576393 -1.356167 -0.650551 27 C -4.675031 -2.241459 -0.682976 28 C -4.600767 -3.467346 0.050888 29 C -3.399066 -3.771294 0.725971 30 C -2.338269 -2.899369 0.705744 31 B 0.000001 2.722907 -0.920495 32 B 0.000001 -2.722909 0.920491 33 O -1.167845 3.339304 -1.273767 34 O 1.167846 3.339308 -1.273758 35 O -1.167844 -3.339309 1.273759 36 O 1.167847 -3.339309 1.273757 37 C -5.715786 4.346158 -0.033871 38 C -6.845681 4.028591 0.678634 39 C -6.918678 2.818265 1.411380 40 C -5.858487 1.947297 1.414212 41 C -5.858490 -1.947295 -1.414208 42 C -6.918682 -2.818261 -1.411375 43 C -6.845684 -4.028588 -0.678630 44 C -5.715789 -4.346157 0.033872 45 C 5.715788 -4.346158 0.033860
46 C 6.845683 -4.028589 -0.678645 47 C 6.918679 -2.818262 -1.411389 48 C 5.858487 -1.947295 -1.414219 49 C 5.858486 1.947296 1.414221 50 C 6.918677 2.818263 1.411391 51 C 6.845680 4.028591 0.678648 52 C 5.715786 4.346159 -0.033857 53 H -3.274819 4.720997 -1.232674 54 H -3.654087 0.437241 1.215132 55 H 3.654087 0.437240 1.215136 56 H 3.274820 4.721001 -1.232661 57 H 3.274822 -4.721000 1.232662 58 H 3.654088 -0.437240 -1.215137 59 H -3.654090 -0.437241 -1.215131 60 H -3.274819 -4.720999 1.232670 61 H -5.658871 5.275653 -0.590228 62 H -7.690746 4.707876 0.684758 63 H -7.817924 2.583494 1.969226 64 H -5.911455 1.017103 1.969786 65 H -5.911459 -1.017100 -1.969781 66 H -7.817929 -2.583490 -1.969219 67 H -7.690750 -4.707873 -0.684753 68 H -5.658873 -5.275652 0.590228 69 H 5.658874 -5.275653 0.590215 70 H 7.690748 -4.707874 -0.684770 71 H 7.817924 -2.583490 -1.969236 72 H 5.911455 -1.017099 -1.969792 73 H 5.911454 1.017100 1.969793 74 H 7.817922 2.583492 1.969238 75 H 7.690745 4.707876 0.684774 76 H 5.658871 5.275655 -0.590213 Optimized TS-2 Tag Symbol X Y Z 1 C 1.241943 -0.588274 0.091458 2 C 0.011388 -1.229358 -0.139474 3 C -1.261624 -0.618745 -0.048011 4 C -1.275076 0.804763 0.182985 5 C -0.009965 1.465077 0.080498 6 C 1.250726 0.823853 0.007101 7 C -2.443988 1.719345 0.374757 8 C -2.332148 3.126067 0.070234 9 C -3.679227 1.355561 0.890616 10 C -3.403493 3.984995 0.096241 11 C -4.798896 2.212935 0.972502 12 C -4.677283 3.558674 0.518875 13 C -2.371537 -1.586550 -0.349702 14 C -3.592141 -1.705980 0.295048 15 C -2.132547 -2.611574 -1.342049 16 C -4.634626 -2.561748 -0.135327 17 C -3.132029 -3.408197 -1.838947 18 C -4.430450 -3.378660 -1.286092 19 C 2.452525 1.647647 -0.291210 20 C 2.367231 3.077395 -0.269691 21 C 3.670849 1.123059 -0.706930 22 C 3.454748 3.886946 -0.495794 23 C 4.803872 1.919340 -0.973391 24 C 4.708466 3.339125 -0.832624 25 C 2.379663 -1.496193 0.357980 26 C 3.378316 -1.206155 1.271120 27 C 2.390915 -2.792515 -0.243420 28 C 4.425297 -2.110485 1.555052 29 C 3.403148 -3.689068 -0.012332 30 C 4.451641 -3.374733 0.882712 31 B 0.011182 2.988235 -0.055784 32 B 0.169190 -2.521193 -0.953596 33 O 1.169745 3.708514 -0.090243 34 O -1.130118 3.712716 -0.202120 35 O 1.364874 -3.173552 -1.073175 36 O -0.860483 -2.929434 -1.753297 37 H -3.224543 5.020151 -0.168952 38 H -3.811230 0.376143 1.294072 39 H 3.311266 4.960075 -0.452698 40 H 3.780461 0.058062 -0.835561 41 H 3.369484 -0.249300 1.779715 42 H 3.369781 -4.652362 -0.507461 43 H -2.873250 -4.129691 -2.604782 44 H -3.764330 -1.185462 1.218818 45 C 5.514181 -4.274869 1.158539 46 C 6.499801 -3.942527 2.055108 47 C 6.473290 -2.694073 2.723053 48 C 5.459759 -1.801454 2.479758 49 H 5.436978 -0.842883 2.987215 50 H 5.533680 -5.232786 0.649875 51 H 7.305717 -4.639098 2.256979 52 H 7.258842 -2.446934 3.427857 53 C 6.045586 1.348659 -1.368725 54 C 7.138828 2.143607 -1.601750
55 H 8.082002 1.699580 -1.898701 56 C 7.043300 3.550092 -1.454279 57 H 7.915656 4.166239 -1.641451 58 C 5.858713 4.134302 -1.080796 59 H 5.784870 5.211270 -0.974195 60 H 6.114747 0.271309 -1.475175 61 C -5.884976 -2.618988 0.534616 62 C -6.896662 -3.420601 0.064950 63 H -7.850617 -3.451306 0.578648 64 C -6.700275 -4.208381 -1.094058 65 H -7.508025 -4.833346 -1.458000 66 C -5.494066 -4.192794 -1.752151 67 H -5.337671 -4.809539 -2.630628 68 H -6.034547 -2.011874 1.421457 69 C -5.809700 4.412303 0.571182 70 C -7.006398 3.950652 1.061664 71 H -7.867467 4.608563 1.097580 72 C -7.127483 2.618632 1.527669 73 H -8.078560 2.271241 1.914547 74 C -6.048277 1.771670 1.486285 75 H -6.141398 0.749163 1.836278 76 H -5.713761 5.434977 0.222642 Optimized 1 Tag Symbol X Y Z 1 C -1.213412 0.705859 0.000263 2 C -1.213412 -0.705859 0.000264 3 C 0.000000 -1.389250 0.000330 4 C 1.213412 -0.705859 0.000262 5 C 1.213412 0.705859 0.000262 6 C 0.000000 1.389250 0.000329 7 C -2.431969 1.433865 0.000107 8 C 2.431969 1.433865 0.000106 9 C -2.406833 2.866436 -0.000053 10 C -3.586809 3.558198 -0.000081 11 C -4.837807 2.869294 -0.000028 12 C -4.876402 1.436876 -0.000007 13 C -3.646899 0.724744 0.000074 14 C 3.646899 0.724744 0.000073 15 C 4.876402 1.436876 -0.000008 16 C 4.837807 2.869294 -0.000028 17 C 3.586809 3.558198 -0.000081 18 C 2.406833 2.866436 -0.000054 19 C -2.431969 -1.433865 0.000108 20 C 2.431969 -1.433865 0.000106 21 C 2.406833 -2.866436 -0.000054 22 C 3.586809 -3.558198 -0.000081 23 C 4.837807 -2.869294 -0.000028 24 C 4.876402 -1.436876 -0.000008 25 C 3.646899 -0.724744 0.000073 26 C -3.646899 -0.724744 0.000074 27 C -4.876402 -1.436876 -0.000007 28 C -4.837807 -2.869294 -0.000028 29 C -3.586809 -3.558198 -0.000081 30 C -2.406833 -2.866436 -0.000053 31 B 0.000000 2.898955 0.000125 32 B 0.000000 -2.898955 0.000125 33 O -1.209225 3.566602 -0.000091 34 O 1.209225 3.566602 -0.000092 35 O -1.209225 -3.566602 -0.000091 36 O 1.209225 -3.566602 -0.000092 37 C -6.059188 3.576001 -0.000072 38 C -7.258603 2.894146 -0.000096 39 C -7.293138 1.493675 -0.000077 40 C -6.122997 0.737773 -0.000046 41 C -6.122997 -0.737773 -0.000046 42 C -7.293137 -1.493675 -0.000078 43 C -7.258603 -2.894146 -0.000097 44 C -6.059188 -3.576001 -0.000072 45 C 6.122997 0.737773 -0.000046 46 C 7.293137 1.493675 -0.000077 47 C 7.258603 2.894146 -0.000096 48 C 6.059188 3.576001 -0.000071 49 C 6.059188 -3.576001 -0.000071 50 C 7.258603 -2.894146 -0.000096 51 C 7.293137 -1.493675 -0.000077 52 C 6.122997 -0.737773 -0.000046 53 H -3.569915 4.641503 -0.000143 54 H 3.569915 4.641503 -0.000143 55 H 3.569915 -4.641503 -0.000143 56 H -3.569915 -4.641503 -0.000143 57 H -6.042574 4.660227 -0.000097 58 H -8.192099 3.445611 -0.000130 59 H -8.258680 1.005355 -0.000096 60 H -8.258680 -1.005355 -0.000096 61 H -8.192099 -3.445611 -0.000130 62 H -6.042574 -4.660227 -0.000097 63 H 8.258680 1.005355 -0.000096
64 H 8.192099 3.445611 -0.000129 65 H 6.042574 4.660227 -0.000096 66 H 6.042574 -4.660227 -0.000096 67 H 8.192099 -3.445611 -0.000129 68 H 8.258680 -1.005355 -0.000096 8. References
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9. NMR and MS Spectra
Figure S14. 1H NMR spectrum of compound 4 (300 MHz, CD2Cl2, 298 K).
Figure S16. 1H NMR spectrum of compound 5 (300 MHz, C2D2Cl4, 298 K).
Figure S18. High-resolution MALDI-TOF MS spectrum of compound 2. Inset: the
